In the field of powered-driven vehicles such as lawn mowers, it is known to provide various belts and pulleys in order to transfer power from one rotating shaft, such as an engine drive shaft, to another rotating shaft, such as a shaft holding a grass cutting blade or other driven element. Examples in the prior art of such systems are as shown in U.S. Pat. Nos. 4,058,957, 4,300,332, 4,307,558, and 4,409,779.
In such systems, due to the preference for rubber or other elastomeric belts, some provision must be given for stretch or wear of the belts. If such a provision is not made, the belt may become loose or disengaged from its supporting pulleys. Furthermore, if the belt is to be selectively clutched and declutched by a drive pulley to provide selection power transfer through the belt, some provision can be made to allow selective slippage of the belt relative to the drive pulley. Finally, as brakes are often used in such configurations a need always exists to provide improved brake performance.
In reference to U.S. Pat. No. 4,058,957, it may be seen that a belt 27 is used to transfer power from a drive pulley 31 to a driven pulley 29, both rotating about substantially parallel axes which are fixed relative to the mower frame. An idler pulley 33 is pivotably attached relative to the mower frame, and provides the function of taking up slack in the belt caused by wear or heat, and also the. clutching function described above.
In reference to U.S. Pat. No. 4,300,332 assigned to McDonough Power Equipment, as may be seen, a driven blade pulley 30 is driven by a belt 32 which is driven by an unshown engine pulley. An idler pulley 34 provides the belt take-up and clutching function described above. A part of FIG. 1 is included in the present application as FIG. 6, denoted as "PRIOR ART".
In comparison, U.S. Pat. Nos. 4,307,358 and 4,409,779 disclose the use of a two-pulley design, in which a movable idler pulley 87 provide the take-up and clutching functions described above, with a second pulley having independently rotatable or "split" sheaves 35, 51, such that engagement of the belt causes the two sheaves 35, 51, to move together by being clutched by the belt 85.
Although some of the above-referenced prior art systems have advantages, shortcomings still exist, namely with respect to the ability of prior art systems to take up excessive slack in a belt, or to discourage further use of the clutching mechanism after a blade brake becomes unacceptably worn.